Article 1. Generally - California Vehicle Code Section 22358.4

22358.4. (a) (1) Whenever a local authority determines upon the
basis of an engineering and traffic survey that the prima facie speed
limit of 25 miles per hour established by paragraph (2) of
subdivision (a) of Section 22352 is more than is reasonable or safe,
the local authority may, by ordinance or resolution, determine and
declare a prima facie speed limit of 20 or 15 miles per hour,
whichever is justified as the appropriate speed limit by that survey.
(2) An ordinance or resolution adopted under paragraph (1) shall
not be effective until appropriate signs giving notice of the speed
limit are erected upon the highway and, in the case of a state
highway, until the ordinance is approved by the Department of
Transportation and the appropriate signs are erected upon the
highway.
(b) (1) Notwithstanding subdivision (a) or any other provision of
law, a local authority may, by ordinance or resolution, determine and
declare prima facie speed limits as follows:
(A) A 15 miles per hour prima facie limit in a residence district,
on a highway with a posted speed limit of 30 miles per hour or
slower, when approaching, at a distance of less than 500 feet from,
or passing, a school building or the grounds of a school building,
contiguous to a highway and posted with a school warning sign that
indicates a speed limit of 15 miles per hour, while children are
going to or leaving the school, either during school hours or during
the noon recess period. The prima facie limit shall also apply when
approaching, at a distance of less than 500 feet from, or passing,
school grounds that are not separated from the highway by a fence,
gate, or other physical barrier while the grounds are in use by
children and the highway is posted with a school warning sign that
indicates a speed limit of 15 miles per hour.
(B) A 25 miles per hour prima facie limit in a residence district,
on a highway with a posted speed limit of 30 miles per hour or
slower, when approaching, at a distance of 500 to 1,000 feet from, a
school building or the grounds thereof, contiguous to a highway and
posted with a school warning sign that indicates a speed limit of 25
miles per hour, while children are going to or leaving the school,
either during school hours or during the noon recess period. The
prima facie limit shall also apply when approaching, at a distance of
500 to 1,000 feet from, school grounds that are not separated from
the highway by a fence, gate, or other physical barrier while the
grounds are in use by children and the highway is posted with a
school warning sign that indicates a speed limit of 25 miles per
hour.
(2) The prima facie limits established under paragraph (1) apply
only to highways that meet all of the following conditions:
(A) A maximum of two traffic lanes.
(B) A maximum posted 30 miles per hour prima facie speed limit
immediately prior to and after the school zone.
(3) The prima facie limits established under paragraph (1) apply
to all lanes of an affected highway, in both directions of travel.
(4) When determining the need to lower the prima facie speed
limit, the local authority shall take the provisions of Section 627
into consideration.
(5) (A) An ordinance or resolution adopted under paragraph (1)
shall not be effective until appropriate signs giving notice of the
speed limit are erected upon the highway and, in the case of a state
highway, until the ordinance is approved by the Department of
Transportation and the appropriate signs are erected upon the
highway.
(B) For purposes of subparagraph (A) of paragraph (1), school
warning signs indicating a speed limit of 15 miles per hour may be
placed at a distance up to 500 feet away from school grounds.
(C) For purposes of subparagraph (B) of paragraph (1), school
warning signs indicating a speed limit of 25 miles per hour may be
placed at any distance between 500 and 1,000 feet away from the
school grounds.
(D) A local authority shall reimburse the Department of
Transportation for all costs incurred by the department under this
subdivision.